Glow discharge starter

ABSTRACT

The invention relates to a glow discharge starter which is provided with a built-in fuse. According to the invention the fuse has a resilient contact member exerting a pulling force on the part to be melted and this in a direction which is parallel to the wall of a tubular part of the starter in which the glow discharge is effected. In the case of a starter provided with a tightly fitting synthetic material jacket the fuse described may avoid risk of fire.

United States Patent 1191 Vervaart et al.

GLOW DISCHARGE STARTER lnventors: Adrianus-Petrus Vervaart; Cornelis Machiel Verheij; Hermanus Maria Jongerius, all of Emmasingel, Eindhoven, Netherlands U.S. Philips Corporation, New York, NY.

Filed: Dec. 20, 1972 Appl. No.: 316,911

Assignee:

Foreign Application Priority Data Dec. 29, l97l Germany G 71 49 219.8

us. c1 313/151, 313/2 0, 313/226, 7 337/1, 337/22, 337/407 1m. (:1. HOlj 1/88 1111 3,780,327 [451 Dec. 18, 1973 [58] Field of Search 313/151, 226, 210

Primary Examiner-Roy Lake Assistant Examiner-Darwin R. Hostetter Att0rneyF rank R. Trifari [5 7] ABSTRACT The invention relates to a glow discharge starter which is provided with a built-in fuse.

2 Claims, 2 Drawing Figures II/I/I'lI/I E f I I l -g/ GLOW DISCHARGE STARTER The invention relates to a glow discharge starter provided with two connection members and a fuse for rendering a tubular part of the starter, in which the glow discharge is effected, inoperative, said fuse being provided in a satisfactory thermal contact with the said tubular part and also including a resilient member which is under a mechanical pretension.

Glow discharge starters of thiskind are used, for example, for the ignition of low-pressure mercury vapour discharge lamps which are provided with two so-called preheated electrodes. As a rule the glow discharge starter is placed in a connection between one end of one electrode and one end of the other electrode.

In a known glow discharge starter of the kind described the fuse is responsive to a too large thermal development in the tubular part of the starter (the dis charge tube) so that this part of the starter is permanently switched off. This is effected in the case of a defeet.

A drawback of the known glow discharge starter is, however, that the fuse is complicated and is secured in a complicated manner and that furthermore upon melting of the suitable part of the fuse the resilient member performs a movement which is at right angles to the wall of the discharge tube. This simplies that either the contact distance of the electrical contacts of the excited fuse (having operated) can only be rather small which with a view to the conventional relatively high mains voltages of, for example, a few hundred volts may be dangerous and may notably lead to electrical flashover, or that at right angles to the actual discharge tube a relatively large space must be economized to make a large contact distance of the excited fuse possible.

An object of the invention is to provide a glowdischarge starter of the kind described in the preamble in which the contact distance of the excited fuse is relatively large but in which also the space required for this fuse in the excited state involves only a slight dimension in a direction at right angles to the wall of the discharge tube.

According to the invention the melting part of the fuse is secured both to a connecting conductor which leads to the tubular part in which the glow discharge takes place and to a bent spring one end of which is secured to one of the said connection members and whose bend is oriented in such a manner that the direction of the mechanical pretension at the area of the melting part is substantially located in a tangent plane to the tubular part at that area.

An advantage of a glow discharge starter according to the invention is its compact structure and also the simple construction of the fuse.

in an advantageous embodiment of a glow discharge starter according to the invention in which the combination of the fuse and the tubular part in which the glow discharge is effected is provided with a jacket enveloping this combination, the entire jacket is made of an insulating synthetic material.

An advantage of this preferred embodiment is that possible risk of fire of these glow discharge starters provided with synthetic material housings can be eliminated by the fuse. it is to be noted that the use of a synthetic material jacket for glow' discharge starters is known per se.

The invention will be further described with reference to a drawing. This drawing shows a glow discharge starter according to the invention. In FIG. 1 the glow discharge starter is shown in a front view in which a jacket associated with the starter is shown in a longitudinal cross-section. FIG. 2 shows a perspective view of the glow discharge starter (partly exploded view).

The reference numeral 1 denotes a tubular part in view a glow discharge can be generated. To this end this tube is filled with a mixture of rare gases, for example, argon, neon and helium and has two bimetal electrodes one of which is shown in broken lines (see 1a). These electrodes bend towards each other when heat is developed by the glow discharge in tube 1. Normally these contacts will contact each other some time after the commencement of the glow discharge so that then a preheating current can flow in a lamp (not shown) to be ignited by this starter.

One bimetal electrode (la) in tube 1 is electrically connected through a connection 2 of copperclad wire to the connection member 3. Connection 2 passes through an insulation plate (4a) of synthetic material which, combined with a jacket 4 entirely consisting of synthetic material, constitutes a complete envelope for the arrangement. A further conductor 5 leads from the other bimetal electrode (not shown in FIG. 1) in the tube 1 to a metal compound 6 having a low melting point, for example, a soldered joint of tin, lead, cadmium. The other end of this metal compound 6 is secured to a semicircularly bent spring 7 which is secured to a further connection member 8 of the glow discharge starter. The bend of the spring 7 is located substantially in a tangent plane at the area of the compound 6 to the cylindrical outer wall of the tube 1. Consequently the direction of the pulling force exerted by the spring 7 on the metal compound 6 (mechanical pre-tension) is also located in this tangent plane. ln the case described this force acts approximately parallel to the longitudinal axis of the tubular part 1.

If for some reason or other, for example, by incorrect adjustment of the position of the bimetal electrodes during manufacture the bimetal electrodes cannot contact each other so that a permanent glow discharge is produced therebetween, so much heat will be developed in tube 1 that the metal compound 6, which is in a satisfactory thermal contact with this tube 1, weakens and the spring 7 which is under a mechanical pretension is released and occupies the position 7' shown in broken lines in the drawing. The electrical contact is then interrupted because the metal compound 6 was located in the series circuit of connection member 3, connection 2, bimetal electrode la, the other bimetal electrode, conductor 5, compound 6 and spring 7 to connection member 8. By this fuse it is prevented that the synthetic material jacket 4 is heated to a too high temperature at which it weakens or burns. The distance between the cylindrical wall of the tube 1 and the jacket 4 was only approximately 2 mms.

An advantage of the starter described over a starter in which the discharge tube 1 is short-circuited in case of an interference is that in the case of the described starter an excitation of the fuse renders the entire preheating circuit without current.

lf desired, a capacitor possibly connected in parallel with the discharge tube 1 and arranged within the jacket 4 may also be switched off by the fuse.

In an embodiment other than the one described, for example, the bend of the spring may substantially entirely envelop the discharge tube 1 with the plane of the conductor which leads to the tubular part in which the glow discharge is effected as well as to a bent spring one end of which is secured to one of the said connection members and whose bend is oriented in such a manner that the direction of the mechanical pretension at the area of the melting part is substantially located in a tangent plane to the tubular part at that area.

2. A glow discharge starter as claimed in claim 1 in which the combination of the fuse and the tubular part in which the glow discharge is effected is provided with a jacket enveloping said combination characterized in that the entire jacket is made of an insulating synthetic material. 

1. A glow discharge starter provided with two connection members and a fuse for rendering a tubular part of the starter, in which the glow discharge is effected, inoperative, said fuse being arranged in satisfactory thermal contact with the said tubular part and being also provided with a resilient member which is under a mechanical pretension, characterized in that the melting part of the fuse is secured to a connecting conductor which leads to the tubular part in which the glow discharge is effected as well as to a bent spring one end of which is secured to one of the said connection members and whose bend is oriented in such a manner that the direction of the mechanical pretension at the area of the melting part is substantially located in a tangent plane to the tubular part at that area.
 2. A glow discharge starter as claimed in claim 1 in which the combination of the fuse and the tubular part in which the glow discharge is effected is provided with a jacket enveloping said combination characterized in that the entire jacket is made of an insulating synthetic material. 